1. Field of the Invention
The present invention relates generally to methods and systems for the prevention of myopia acquisition in children and young adults. Myopia, also known as nearsightedness, is a visual defect in which distant objects appear blurred because their images are focused in front of the retina rather than on it causing a retinal blur. Myopia is one of the more prevalent human visual disorders, affecting up to 50% of adults in Western countries in even more in Asia, with associated cost of correction and management having been estimated at several billion dollars per year. In some regions of the world, up to 75% of people may have myopia. Moreover, the prevalence of myopia is even increasing. In some instances, high levels of myopia may result in grave consequences, such as, blindness from retinal detachment, myopic macular degeneration, cataract, glaucoma, or severe side effects or complications from myopia correction. Thus, treatments which inhibit myopia would have a widespread benefit. It is believed that myopia may be caused by environmental factors, particularly intensive and excessive near work, with hereditary/genetic factors further defining susceptibility. Numerous animal studies have demonstrated that prolonged hyperopic defocus triggers an increase in eye growth, typically along an axial length of the eye, which can cause myopic change. Prolonged hyperopic defocus may be caused by naturally occurring refractive errors. Both accommodation deficiencies and life styles or occupations involving intensive near work result in frequent exposure to hyperopic defocus which in turn induces myopia. A number of techniques have been developed over the years to control or prevent myopia progression. These techniques include rigid contact lenses, spectacles, pharmacological delivery of atropine, biofeedback, vision training, and intentional undercorrection. Surgical correction of myopia includes refractive surgery, including myopic keratomileusis, radial keratotomy, and photorefractive keratotomy. While all these techniques have enjoyed varying levels of success, no one of these procedures provides a significant myopia prevention in all cases. Several studies have proven the use of bifocal spectacles or glasses to reduce the rate of myopia progression in children. In light of the above, it would be desirable to provide improved methods and systems for the prevention of myopia acquisition. It would be further desirable if such treatment methods would be safe, inexpensive and effective.
2. Description of Background Art
A significant correlation between nearwork and myopia has been found by Saw et al. (Lancet. 2001 Feb. 3; 357(9253): 390). Schaeffel has found experimentally that axial lengh growth might be influenced with glasses (Ophthalmologe. 2002 February; 99(2): 120-39). Leung and Brown have found that wearing progressive lenses slowed progression of myopia (Optom-Vis-Sci. 1999 June; 76(6): 346-54).